A conventional rotating tool holder disclosed in CH 692 449 includes a cutting head and a shank, which has two mating pins. The mating pins transmit rotational torque with the help of a locking bolt. However, the pins are not easy to disassemble and may be broken during machining.
Other conventional modular type boring bars do not have any structural elements for torque transmission. Therefore, the coupling screws directly bear the stress resulting from the boring rotation, and are vulnerable to breakage.